The present invention relates to a plate lockup mechanism for use in securing a printing plate to a printing cylinder.
Various means have been used in the past to secure a flexible printing plate to a printing cylinder. Plate lockup mechanisms are generally located within a gap in the printing cylinder. The printing plate is wrapped around a cylinder, and the opposite ends of the plate are inserted into the gap to be engaged by the lockup mechanism. The smaller the gap in the cylinder, the larger the print area for a given size cylinder, or for a given print area, the plate cylinder and consequently the entire press, may be made smaller.
The presence of the gap in the cylinder causes the cylinder to vibrate as the gap rotates through a nip formed by the printing cylinder and a cooperating cylinder. In order to minimize this vibration, it is desirable that the gap in the cylinder through which the ends of the printing plate are inserted be as small as practicable. U.S. Pat. Nos. 2,775,198 and 3,012,841 show typical plate clamp mechanisms.
Also an additional consideration in the design of a plate lockup mechanism is that in many presses the cylinders may be rotated in either direction depending on what path a web to be printed on takes through the press. Accordingly, it is desirable for a plate lockup mechanism to be effective regardless of the direction of rotation of the cylinder. Further, it is desirable for a plate clamp mechanism to be able to be used in presses where plural plates are located circumferentially around the cylinder. U.S. Pat. Nos. 1,795,700; 1,795,702; and 3,727,551 disclose such plate lockup mechanisms.